In the related art, with regard to a drive assist device, for example, as disclosed in Japanese Unexamined Patent Application Publication No. 6-243399, a vehicle-to-vehicle distance warning device that measures a vehicle-to-vehicle distance between a host vehicle and a preceding vehicle, calculates a safety vehicle-to-vehicle distance in which the host vehicle does not collide with the preceding vehicle using a host vehicle speed and the vehicle-to-vehicle distance, and generates an alarm in a case where the vehicle-to-vehicle distance is shorter than the safety vehicle-to-vehicle distance.